The effect of coupling agent and chemical treatment on rice husk ash‐ filled natural rubber composites

Abstract

Rice husk ash was incorporated into natural rubber (NR) using a laboratory size two-roll mill. Curing using a conventional vulcanization system (CV) was chosen, and cure studies were carried out on a Monsanto rheometer. Physical testing of the NR vulcanizates involved the determination of tensile, tear, and abrasion resistances, and hardness. Fourier transform infrared spectroscopy (FTIR) analysis was done to verify the presence of the characteristic functional groups of precipitated silica in MHA (milled husk ash) and THA (treated husk ash). The effect of the coupling agent, bis(3-triethoxysilylpropyl)-tetrasulfane (Si-69), on the curing and physical properties of the vulcanizates was investigated. A chemical treatment on a rice husk ash was done, and the effects of this procedure are also reported. For comparison, two commercial fillers, precipitated silica (Zeosil-175) and carbon black (N774), were also used. Although the presence of the silane coupling agent had not brought the expected increase in properties, treated husk ash showed exceptional performance in terms of tensile strength and abrasion resistance of the filled vulcanizates.

Possibilities of rice husk ash to be used as reinforcing filler in polymer sector -a review

“…In the same way, Ismail et al [79] also found an increase of the tensile strenght as WRHA increased, until a maximun of 10 phr. This behavior is in accordance with Costa et al [101] which is attributed to the possible particles agglomeration, as commented above.…”

“…As a result, the composites filled at 20 phr with treated RHA showed a higher tensile strength as compared with the NR filled at 20 phr with commercial silica (Zeol-175), and even higher than the Zeol-175/NR composite compatibilized with Si-69 [101]. In the same way, Ismail et al [79] also found an increase of the tensile strenght as WRHA increased, until a maximun of 10 phr.…”

“…Many researchers have been studying the use of RHA as filler in natural and/or synthetic rubber [81]- [83], [101], [102]. Overall results indicate that RHA can be used as a cheap filler for natural rubber materials where high quality mechanical properties are not required.…”

“…For instance, Costa et al [101] reported that the tensile strength of milled RHA/NR vulcanized composites increase with the increasing filler content until a maximum level reached at 20 phr. The reduction of this property at higher loads may be caused by filler particles agglomeration that leads to poor polymer-filler compatibility.…”

“…For instance, Da Costa et al [101], showed a treatment with 20 wt.% NaOH and 12 M HCl in order to improve the mechanical properties of NR filled with RHA. As a result, the composites filled at 20 phr with treated RHA showed a higher tensile strength as compared with the NR filled at 20 phr with commercial silica (Zeol-175), and even higher than the Zeol-175/NR composite compatibilized with Si-69 [101].…”